Underreaming tool



Oct. 1, 1963 I v; D. STONE ETAL UNDERREAMING TOOL 2 Sheets-Sheet 1 Filed July 15. 1960 H m 5 a m M55 7 A K/ Z R f Y B 3 4 6 4 Z 7 K r r 3 2 Sheets-Sheet 2 Filed July 15. 1960 INVENTORS KIRK 1Q. SH/QZEV BY V/IQG/L 0. STU/V5 ATTORNEY United States Patent 3,105,562 EHJDERREAWHP'IG TtiG-L Virgil D. Stone, Morgan City, 1121., and K ll: R. Shirley, Long Beach, Calif; said Stone assignor to Gull {lit Corporation, Pittsburgh, Fan, a corporation of lennsylvania, and said Shirley assignor to The fiervco (1cmpany, Long Beach, (Zalih, a company of Nevada Filed July 15, 196%, Ser. No. 43,111 5 Claims. or. l752e3) This invention relates to the drilling of wells and more particularly to an underreaming tool for enlarging the borehole of a well.

Frequently it is desirable to enlarge the diameter of a borehole below a string of casing in a well, for exampie, to provide space for gravel packing a slotted liner. The enlmgement is ordinarily accomplished by use of an underreamer which has cutting elements which can be moved to an extended position after the underreamer is lowered to a depth below the casing.

Recently a method of drilling oil and gas wells has been developed in which all drilling, after the surface casing has been set, is performed through a single blowout preve-nter assembly. in that method of drilling, it is desirable to use a small blowout preventer capable of with standing high pressures which may be encountered during later stages of the drilling. A borehole having a diameter larger than the maximum opening of the blowout preventer may be necessary to provide space for efiective cement ng of the largest stringof casing that is to be run through the blowout preventer; hence, it becomes necessary to underream a portion of the borehole at the upper end of the well. The shallow formations in which the largest size of casings are set often are less competent than those at greater depths and are more subject to collapse of the borehole wall. It is desirable to provide an under-reaming tool in which the underreaming blades can be maintained in a fixed extended position as the tool is withdrawn from the well to allow checking of the borehole diameter and yet which can be collapsed to permit the tool to pass through the blowout preventer.

This invention resides in an underreamer tool having cutting elements which are moved outwardly to an eX- tended position by a cam movable vertically by fluid pressure within the underrearner tool. Locking means prevent movement of the cam during use of the tool and while the tool is being withdrawn from the well to hold the cutting elements in the extended position. Means are provided for exerting fluid pressure in the tool to overcome the locking means and move the cam to a lower position permitting the cutting elements to return to the retracted position.

In the drawings:

FIGURE 1 is an elevation, partially in vertical section, of the underreamer tool of this invention showing the underrearner with the cutting elements locked in the extended position.

FIGURE 2 is an elevation, similar to FlGURE 1, of the underreamer tool with the cutting elements in the retracted position.

Referring to FIGURE 1 of the drawings, the underreamer tool indicated generally by reference numeral has a tubular upper body member 12 connected at its lower end by means of screw threads 14 to a tubular lower body member 16. The upper body member 12 is internally threaded at 18 for connection to a section of drill pipe, not shown, on which the tool is lowered into the well and rotated. The lower end of the lower body member 16 is threaded as indicated at 20 for connection to a conventional drilling bit, the shank Olf which is shown in the drawings and indicted by reference numeral 22.

Vertically slideable within the underrearner 10 is a ice tubular liner 24 having a sleeve 26 securely mounted on its lower end. The sleeve 26 is provided with a tapered cam surface 23 at its upper end adapted to engage cutter arms or the underreamer in the manner herein-after described. Also vertically slideable within the upper body member 12 of the underreamer tool is a tubular piston 30 immediately above the upper end of the liner 24-. The piston 30 has a larger outside diameter than the liner 24 and is adapted to slideably engage the inner wall of the upper body member 12. Leakage downwardly along the outer wall of the piston 30 is prevented by sealing means 32 at the upper end of the piston 3t) and leakage upwardly along the outer wall of the piston is prevented by sealing means 34 at the lower end of the piston. Leakage downwardly between the upper end of the liner 24 and the lower end of piston 30 is prevented by sealing means 35 and upwardly between the liner 24 and the upper body member 12 by sealing means 37.

The sleeve 26 his slideably along the inner wall of the lower body member 16 of the underreamer tool 16. The central opening in the lower body member 16 of the underreamer tool below the connection with the upper body member has a diameter larger than that of the central opening in the upper body member 12. Hence, the ar a or" the combined sleeve 26 and liner 24 at the lower end of the liner is larger than the area of the upper end of the piston. Fluid pressure within the underreamer tool 19 will, there-fore, exert a net upward force on the liner 24. Leakage around the outer surface of the sleeve 26 is prevented by sealing means 38. The liner 24 and sleeve 26 are securely fastened together by suitable means, such as Welding, to form a unitary structure. The piston 3Q bears against the upper end of the liner 24 and, in eifect, forms an upper extension of the liner.

A plurmity of cutter arms 4-9 pivot on pins 42 at the upper ends of the cutter arms. Pins 4-2 extend across slots in the wall of the lower body member 16 adapted to receive the cutter arms 49. The cutter arms 40 are provided on their outer faces with cutting elements for engagement with the borehole wall during the operation of the underreaming tool. The cutting elements 44 illus trated in the drawings are of the blade-type; however, this invention is equally useful in underreamer tools having rock bit-type cutting elements and those having bladetype cutting elements. Outward movement of the cutting arms 46 is limited by engagement of a lip 46 on their lower end with a shoulder 48 extending upwardly from the lower end of the slot in which the cutter arm is mounted. I

In order to drill a hole of uniform gage, it is important to prevent lateral movement of the cutting elements 44 with every increase or decrease of the fluid pressure within the underreamer tool. For this reason locking means, indicated generally by 4?, are provided to maintain the cutter arms 4%, and hence the cutting elements 4-4, in the fully extended position during the underreaming operation. The locking means illustrated in the drawings consists of a ball-type latching member 50 mounted in a socket 52 in the wall of the lower body member 16 of the underreamer tool. A compressed helical spring 54 within the socket 52 engages the inner end of the ball 50 and in turn is held in place in the socket by a threaded plug 56. The compressed helical spring urges the ball 58 into a depression Ed in the outer surface of the sleeve 26. A plurality of such locking means may be provided if necessary to hold the conical sleeve 26 in the upper position.

Locking means similar to those illustrated for the sleeve 26 engage the piston 35} to hold it in the upper position. A ball 60 is urged by a helical spring 62, held in place in a socket 64 by a threaded plug 66, into a dimple 68 properly located in the outer surface of the piston 3b to lock it in the upper position.

in the operation of the underreamer tool of this invention, the tool is preferably used to underream a section of the hole simultaneously with drilling. For such use, the underreamer tool it} is assembled with the liner 24 in the lower position illustrated in FlGURE 2 of the drawings. A drill bit is connected to the lower end of the underrearner tool and the upper end of the underrearner tool is connected to the lower end of a joint of drill pipe. The tool is lowered into the hole on drill pipe to the elevation at which the underreaming is to begin and drilling mud pumped down through the drill pipe and through the tool. The pressure within the tool resulting from the resistance to flow through the orifices of the drill bit exerts a force against the lower end of the liner 24 and sleeve 2a which overcomes the force exerted against the upper end of the piston 3d and moves the liner and sleeve upwardly. The cam surface 23 of the sleeve 2t, engages the inner face of the cutter arms .4} and moves the cutter arms, and consequently the cutting elements 44, outward 1y. When the liner 24 and sleeve 26 move to the extreme upper position illustrated in FIGURE 1, ball 5% enters the depression 58 and locks the sleeve 26 in the upper position to hold the cutting elements 44 in the fully extended position. Similarly, the ball 64 enters the dimple 68 in the outer surface of the piston St to lock the piston 3A) in the upper position.

The drilling and underreaming are accomplished in the usual manner by simultaneously pumping a drilling mud downwardly through the drill pipe, the underreamer, and the drill bit while rotating the assembly, whereupon the drill bit and the cutting elements of the underreamer cut the hole to the desired diameter. After the borehole has been drilled and underreamed to the desired depth, the tool is pulled from the hole.

The locking of the cutting elements in the extended position provides a test for drag as the tool is pulled which will show whether or not the underreamed borehole has maintained the proper gauge. If the blades drag during the withdrawal of the underrearning tool, the underreaming can be repeated to again ream sections of the hole that have not maintained proper gauge. It is important that the underreamed portion of the borehole have at least the diameter of the underreamer to allow casing to be run into the hole and to provide space for efiective cementing of the casing.

After the underreamed portion of the borehole has been tested and re-underreamed if necessary, a ball 79 is dropped down the drill pipe to seat on a beveled upper surface 72 of the piston 39. Fluid pressure is then applied in the drill pipe and against the ball '72 until the force exerted against the upper end of the piston is transmitted through the balls 5-1 and 6 to compress the helical springs and thereby release the locking means. The force of the fluid against the ball 74? and the piston 39 moves the liner 24 and sleeve 2s downwardly to a lower position and the cutter arms 4t? drop to the retracted position illustrated in FIGURE 2 of the drawings. The underreamer then can be lifted through the blowout preventer or, if the underreaming is to enlarge a hole below casing to a diameter larger than the casing, through the casing.

The underreaming tool of this invention is particularly useful when it is desirable to enlarge the upper part of the borehole of a Well. The locking means not only prevents variations in the position of the cutter arms because of variations in the pressure of the drilling fluid, but maintain the cutter arms in the extended position as the tool is pulled upwardly through the well, thereby providing a test for the diameter of the borehole.

We claim:

1. An underreaming tool for enlargement of the borehole of a well, said tool compr' a rigid tubular body adapted to be connected to a string of drill pipe, said tubular body having a central opening extending longitudinally therethrough, the diameter of said central opening being larger at its lower end than at its upper end, a plurality of slots spaced around the circumference of said tubular body and extending through the wall thereof, cutting elements pivotally mounted on the tubular body for movement from a retracted position extending into the slots to an extended position, a liner slidable within the tubular body from a lower to an upper position, an outwardly sloping cam integral with said liner adapted to the cutting elements and move them to an extended position on upward movement of the liner, sealing means engaging the liner and tubular body to prevent flow of fluid therebetween, the lower end of said liner having a larger area than the upper end of said liner whereby fluid pressure within the tubular body produces an upwar force on the liner to move the liner to the upper position to extend the cutting elements, locking means engaging the liner and tubular body to lock the liner at the upper position with the cutting elements extended, said locking means being releasable by downward force on the liner to permit movement of the linerto a lower position.

2. An underreaming tool for enlargement of the borehole of a well, said tool comprising a rigid tubular body adapted to be connected to a string of drill pipe, said tubular body having a central opening extending longitudinally therethrough, the diameter of said central opening being larger at its lower end than at its upper end, a plurality of slots spaced around the circumference of said tubular body and extending through the wall thereof, cutting elements pivotally mounted on the tubular body for movement from a retracted position extending into the slots to an extended position, a liner slidable within the tubular body between a lower position and an upper position, an outwardly sloping cam integral with said liner adapted to engage the cutting elements and move them to an extended position on upward movement of the liner, sealing means engaging the liner and tubular body to prevent how of fiuid therebetween, the lower end of said liner having a larger area than the upper end of said liner whereby fluid pressure within the tubular body produces an upward force on the liner to move the liner to the upper position to extend the cutting elements, locking means engaging the liner and tubular body to lock the liner at the upper position with the cutting elements extended, a seat at the upper end of the liner adapted to receive a plug and thereby restrict flow through the liner whereby hydraulic force within the drill pipe above the liner releases the locking means and moves the liner downwardly to retract the cutting elements.

3. An underreaming tool for enlarging the borehole of a well, said tool comprising a rigid tubular body adapted to be connected in a string of drill pipe and having slots extending through the outer wall thereof, cutting elements pivotally mounted in the slots for movement outwardly from a retracted position to an extended position beyond the wall of the tubular body, a liner slidable within the tubular body between a lower position and an upper position, said liner extending within the tubular body from a level above the slots to a level below the slots, an outwardly sloping cam surface on the outer surface of the liner positioned to engage the cutting elements whereby upward movement of the liner causes the cutting elements to move to the extended position, first sealing means engaging the liner and the tubular body above the slots, second sealing means engaging the liner and tubular body below the slots, the lower end of said liner having a larger area than the upper end of said liner whereby the pressure of the drilling fluid circulating down the drill pipe causes the liner to move to an upper position at which the cutting elements are extended, locking means engaging tr e tubular body and liner to lock the liner in the u r position, lock ng being releasable by the application of force to the upper end of the liner whereby the cam surface moves downwardly permitting the cutting elements to move to the retracted position.

4. An underreaming tool as set forth in claim 1 in which the locking means comprise a depression in the outer surface of the liner, a ball mounted in a socket in the tubular body in a position to enter the depression in the liner when the liner is at its uppermost position, and resilient means in the socket in the tubular body urging the ball against the liner.

5. An underreaming tool for enlargement of the borehole of a well, comprising a rigid tubular body adapted to be connected to a string of drill pipe above a drill bit at the lower end of the string of drill pipe, said tubular body having a central opening therethrough, the diameter of the lower end of the central opening being larger than the diameter of the upper end of the central opening, a tubular liner slidably mounted within the tubular body, said tubular liner having a large central opening of substantially uniform diameter throughout its length extending therethrough to allow substantially unimpeded fiow of drilling fluid through the tubular body to the drill bit, the lower end of the liner having a larger outer diameter than the upper end of the liner whereby fluid pressure within the tubular body exerts a net upward force on the liner, slots spaced circumferentially around the tubular body extending through the wall thereof, cutting members pivotally mounted on the tubular body for movement radially outward beyond the tubular body from a retracted position in the slots to an extended position, an outwardly sloping cam surface on the outer surface of the liner adapted to engage the cutting members on upward movement of the liner to move the cutting members to the extended position, locking means engaging the tubular body and the liner, compressed resilient means in the tubular body engaging the locking means and urging said locking means against the liner to lock the liner at an upper position with the cutting members fully extended, and a seat at the upper end of the liner adapted to receive a plug to restrict flow through the liner whereby hydraulic pressure applied above the liner exerts a downward force to overcome the locking means and move the liner within the tubular body to a lower position whereby the cutting members move to the retracted position.

References Cited in the file of this patent UNITED STATES PATENTS 1,786,484 Duda Dec. 30, 1930 1,921,135 Santiago Aug. 8, 1933 2,169,502 Santiago Aug. 15, 1939 2,457,628 Baker Dec. 28, 1948 2,699,921 Garrison Jan. 18, 1955 2,719,701 Kammerer Oct. 4, 1955 2,809,016 Kammerer Oct. 8, 1957 

